1. Field of the Invention
The present invention relates to an electric-component mounting system arranged to mount electric components (typically, electronic components), and more particularly to techniques for reducing vibrations in the system.
2. Discussion of Related Art
JP-A-11-11446 discloses an example of an electric-component mounting system wherein various working devices necessary to mount electric components on a circuit substrate are disposed on a common main body of the system. In the electric-component mounting system disclosed in the above-identified publication, the working devices disposed on the common main body of the system include: a component-supplying device operable to supply electric components; a printed-wiring-board holding device operable to hold the circuit substrate in the form of a printed-wiring board; a holding-device positioning device operable to move or position the printed-wiring-board holding device; and a component-mounting device operable to mount the electric components on the printed-wiring board.
The component mounting device includes a plurality of mounting head, and a head turning device operable to turn the mounting heads about a common axis of turning such that the plurality of mounting heads are sequentially moved to and stopped at a plurality of working stations or positions such as: a component-receiving position at which each mounting head receives the electric component from the component supply device; and a component-mounting position at which the mounting head mounts the electric component on the printed-wiring board.
While each mounting head is moved from the component-receiving position to the component-mounting position, the position of the electric component as held by the mounting head is detected by a component-hold-position detecting device disposed at a component-hold-position detecting position, and the mounting head is rotated about its axis by a head-rotating device disposed at a component-hold-position rectifying device, to eliminate an angular positioning error of the electric component. While the mounting head is then moved from the component-mounting position to the component-receiving position, the mounting head is rotated about its axis by another head-rotating device disposed at an angular-head-position resetting device, so that the mounting head is returned to its original angular position in which the mounting head receives the electric component.
The component-supplying device includes a component supply table and a table-positioning device for moving and positioning the component supply table. The component supply table includes a feeder carriage and a plurality of component feeders mounted on the feeder carriage. In operation of the component-supplying device, the component supply table is moved such that component-supply portions of the component feeders are successively aligned with a predetermined component-supply position of the component-supplying device, so that the electric components are supplied from the respective component feeders. The printed-wiring board is positioned by the holding-device positioning device which is operable to move the printed-wiring-board holding device, so that a component-mounting position at which the electric component is to be mounted on the printed-wiring board is located right under the mounting head located at the component-mounting position.
As described above, the plurality of working devices such as the head turning device disposed on the main body of the system are operated to mount the electric components on the printed-wiring board. In one cycle of operation of the system to mount one electric component on the printed-wiring board, the two or more working devices are operated simultaneously. This one cycle of operation includes simultaneous operations of the working devices performed between two moments at which two adjacent mounting heads have reached the component-mounting position. For instance, those simultaneous operations include: a movement of the electric component by each mounting head, which movement takes place due to turning of the mounting heads about the common axis of turning; a positioning movement of the printed-wiring board by the holding-device positioning device; and a positioning movement of the component supply table by the table-positioning device. The simultaneous operations cause different kinds of vibrations of various operating members of the working devices due to acceleration and deceleration upon starting and stopping of linear, rotary and turning movements of the operating members. Those different kinds of vibrations are superimposed on each other, resulting in a relatively large magnitude of vibration of the electric-component mounting system as a whole, which undesirably lowers the accuracy of mounting of the electric components.
In addition, the known electric-component mounting system described above is not arranged in an effort to reduce the magnitude of the overall vibration of the system. Described in detail, if all of the working devices are operated with maximum permissible acceleration and deceleration values, the operating cycle times of the working devices are determined by the maximum permissible acceleration and deceleration values. If any one of the thus determined operating cycle times of the working devices except the head turning device is longer than the cycle time of the head turning device, the head turning device is operated with a cycle time longer than that corresponding to its maximum permissible acceleration and deceleration values. If none of the operating cycle times of the working devices except the head turning device are longer than the cycle time of the head turning device, the electric-component mounting system is operated with the cycle time of the head turning device, and all of the working devices are operated at their maximum permissible acceleration and deceleration values, except where the cycle time of the head turning device is required to be prolonged for some reason or other associated with any other working device. For example, each working device which is operable at one or a plurality of acceleration and deceleration values is operated at its maximum acceleration and deceleration values. In this case, some of the working devices may be operated at unnecessarily high acceleration and deceleration values, causing a relatively large magnitude of vibration. Where the different working devices are simultaneously operated at their maximum permissible acceleration and deceleration values, the required operating times of the working devices are generally different from each other. For instance, the required operating time of one of the working devices is shorter than those of the other working devices where the required amount of operation of the above-indicated one working device is smaller than those of the other working devices. In this instance, the operation of the above-indicated one working device at its maximum permissible acceleration and deceleration values in the known system is unnecessary and undesirable since it merely causes an increase in the magnitude of vibration of the known electric-component mounting system.
The problem described above is encountered not only in the electric-component mounting system of the type wherein the plurality of mounting heads are turned about the common axis of turning by the head turning device, but also in electric-component mounting systems of other types in which electric components are mounted on a circuit substrate by operations of a plurality of working devices, such as a system of a type wherein the electric component is mounted on the circuit substrate by a movement of a mounting head along at least one of two mutually perpendicular axes in a plane parallel to the plane of the circuit substrate.